It is the goal of this work to deduce the basic interactions mediating the formation of rhodopsin from opsin and 11-cis retinal. This goal is derived from the fact that any interactions established during regeneration must be broken on visual excitation. Hence, we anticipate obtaining information on the chemical and structural alterations which initiate the visual process. In addition, rhodopsin is a membrane protein and as such has many properties favorable for obtaining information on the significance and chemistry of protein-membrane interactions. To date we have isolated rhodopsin solubilized by sodium and characterized the chemical and physiological properties of this material. Based on a comparison of the properties of cholate solubilized rhodopsin to rhodopsin bound to the rod disc membrane we feel we have established an adequate model system. Present studies are concerned with characterizing the sodium cholate-rhodopsin micelle and more fully understanding the structural functional relations in this micelle.